linux-kernel - [PATCH v1 net-next 7/7] igc: replace deprecated strncpy with strscpy

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Message-ID: <20231010-netdev-replace-strncpy-resend-as-series-v1-7-caf9f0f2f021@google.com>
Date:   Tue, 10 Oct 2023 22:27:00 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     linux-hardening@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH v1 net-next 7/7] igc: replace deprecated strncpy with strscpy

`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect netdev->name to be NUL-terminated based on its use with format
strings:
|       if (q_vector->rx.ring && q_vector->tx.ring)
|               sprintf(q_vector->name, "%s-TxRx-%u", netdev->name,

Furthermore, we do not need NUL-padding as netdev is already
zero-allocated:
|       netdev = alloc_etherdev_mq(sizeof(struct igc_adapter),
|                                  IGC_MAX_TX_QUEUES);
...
alloc_etherdev() -> alloc_etherdev_mq() -> alloc_etherdev_mqs() ->
alloc_netdev_mqs() ...
|       p = kvzalloc(alloc_size, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>

---
Note: build-tested only.
---
 drivers/net/ethernet/intel/igc/igc_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 98de34d0ce07..e9bb403bbacf 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -6935,7 +6935,7 @@ static int igc_probe(struct pci_dev *pdev,
 	 */
 	igc_get_hw_control(adapter);
 
-	strncpy(netdev->name, "eth%d", IFNAMSIZ);
+	strscpy(netdev->name, "eth%d", sizeof(netdev->name));
 	err = register_netdev(netdev);
 	if (err)
 		goto err_register;

-- 
2.42.0.609.gbb76f46606-goog